The traditional approach to urban design studies has been based on what can be described as a generalised anatomical model, e.g., functional zoning coupled to metaphors such as green areas serving as the ‘lungs’ of cities. Despite the frequent use of biological metaphors, urban design has generally proceeded from an understanding of cities as static arrays of buildings and infrastructures that exist in, but are distinct from, stable environments. But this approach does not reflect the dynamic systems of cities throughout history, nor their close coupling to the dynamics of their local environment, climate and ecology, and now the global dynamics of culture and economy. The limitations of this approach, in which cities are treated as discrete artefacts, rather than nodes interconnected by multiple networks, are compounded by the legal and regulatory boundary of the city usually being defined as an older core, so that cities are regarded as something quite separate from their surrounding territory. All cities have administrative boundaries, but cities are very rarely either physically or energetically contained within those administrative boundaries. In the past, cities gathered most of the energy and materials they needed from their immediate local territory, and trade linked systems of cities across whole regions. The growth and vitality of many cities are no longer dependent on the spatial relationship with their immediate environs but on the regional and global flows of resources. The flow of materials, information and energy through cities comes from far outside their physical and regulatory (municipal) boundaries. Cities now extend their metabolic systems over very great distances, so that the extended territory of the urban metabolism of a city and its geographical ‘place’ are often completely decoupled.

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Geoffrey B. West, James H. Brown and Brian J. Enquist (1997) A General Model for the Origin of Allometric Scaling Laws in Biology
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